Alterations in the epigenome have been shown to be a layer of regulation of gene expression in development and differentiation. Both chromatin modifications and DNA methylation are important in these processes. Relatively little is known about these changes in aging, but from studies done in the laboratory of one of the Co-PIs (EM), alterations in the liver and in melanocytes with age have been documented. This application brings together a multi- disciplinary team to generate a global, genome wide map of chromatin modifications associated with both activation and repression of gene expression as well as a global map of cytidine methylation sites in the DNA. DNA methylation has been shown to have more of a correlation with chromatin modifications than with specific DNA sequence. We propose to carry out these studies on murine hematopoietic stem cells (HSC) which have been shown by the Co-PI (MG) to have significant changes in gene expression between young and old mice as well as reduced ability to engraft upon transplantation to lethally irradiated recipients. The maps will be generated using high throughput sequencing which gives nucleotide level discrimination. Further, to test the role of the IGF1 pathway in chromatin modification, we will examine the HSC from a long lived mouse model, the growth hormone releasing hormone receptor mutant, the Little mouse. In addition, a second model of interest to the aging community that will be studied is the premature aging syndrome in which the p53 protein is stabilized and the animals have a shortened lifespan with accelerated characteristics of aging. Data generated from these studies will be a resource for the aging community and will be made available to the scientific community through the NCBI Gene Expression Omnibus site. This grant will enable the recruitment of four new personnel and can be completed within two years thus fulfilling one of the goals of the ARRA program. PUBLIC HEALTH RELEVANCE: This application will generate data on the epigenome of hematopoietic stem cells with age which will be released to the scientific community immediately. This project requires high throughput technology and a team of multidisciplinary investigators. The grant will respond to the ARRA guidelines by employing four individuals not currently working in the laboratories of the investigators.